LightLight

Part 2Part 2

ReflectionReflection

Occurs when waves traveling in one Occurs when waves traveling in one media reach a boundary with another media reach a boundary with another media and bounce back into the first media and bounce back into the first mediummedium

Total ReflectionTotal Reflection all of the wave energy all of the wave energy is transmitted backis transmitted back

Partial ReflectionPartial Reflection some of the wave some of the wave energy is transmitted into the new mediumenergy is transmitted into the new medium

ReflectionReflection

Amount of reflection is dependent on Amount of reflection is dependent on the rigidity of the mediathe rigidity of the media

Metals Metals very rigid; reflect most light very rigid; reflect most light

Glass/Water Glass/Water not as rigid to light waves; not as rigid to light waves; allows waves to pass through allows waves to pass through

Law of ReflectionLaw of Reflection

Incident waves and reflected waves make Incident waves and reflected waves make equal angles with a line perpendicular to equal angles with a line perpendicular to the surface, called the the surface, called the normal.normal.

Angle of Incidence Angle of Incidence angle made by the angle made by the incidence wave and the normalincidence wave and the normal

Angle of Reflection Angle of Reflection angle made by the angle made by the reflected wave and the normalreflected wave and the normal

MirrorsMirrors

Virtual ImagesVirtual Images images seen in a mirror images seen in a mirror that appear to originate behind the mirrorthat appear to originate behind the mirror

Light does not pass through the image Light does not pass through the image position, but behaves like it doesposition, but behaves like it does

Convex MirrorConvex Mirror creates virtual images creates virtual images smaller and closer to the mirrorsmaller and closer to the mirror

Concave MirrorConcave Mirror creates virtual images creates virtual images larger and farther awaylarger and farther away

MirrorsMirrors

Mirror EquationMirror Equation

1/p + 1/q = 1/f1/p + 1/q = 1/f

p p object distance (d object distance (doo))

q q image distance (d image distance (dii))

f f focal length focal length • Object and image distance are positive when measured Object and image distance are positive when measured

from center of mirror to any point in front of mirrorfrom center of mirror to any point in front of mirror• Object and image heights are positive when above the Object and image heights are positive when above the

principle axis and negative belowprinciple axis and negative below

MirrorsMirrors

Focal Length of a curved mirror is one half Focal Length of a curved mirror is one half the radius of curvaturethe radius of curvature

Concave Mirror Concave Mirror focal length is positive focal length is positive

Convex Mirror Convex Mirror focal length is negative focal length is negative

MirrorsMirrors

Magnification EquationMagnification EquationM = hM = hii/h/hoo = -q/p = -q/p

M is positive when the image is in front of M is positive when the image is in front of the mirror and invertedthe mirror and inverted

M is negative when the image is behind M is negative when the image is behind the mirror and uprightthe mirror and upright

Reflection of SoundReflection of Sound

EchoesEchoes sound reflects better off large, sound reflects better off large, rigid, smooth surfacesrigid, smooth surfaces

reflects less if the surface is reflects less if the surface is irregular irregular and softand soft

AcousticsAcoustics study of the reflective study of the reflective properties of soundproperties of sound

ReverberationsReverberations garbled sound caused garbled sound caused by multiple reflectionsby multiple reflections

RefractionRefraction

The bending of waves that results The bending of waves that results from waves being made to travel from waves being made to travel more slowly (or quickly) than another more slowly (or quickly) than another partpart

Refraction of SoundRefraction of Sound

Refracted due to differences of media or Refracted due to differences of media or difference within a mediadifference within a media

Warm AirWarm Air waves bend away from the waves bend away from the ground and seem to not carry wellground and seem to not carry well

Cold AirCold Air waves bend toward the ground waves bend toward the ground and seem to carry welland seem to carry well

Refraction of LightRefraction of Light

When one part of the ray is made to travel When one part of the ray is made to travel more slowly than another, the rays are more slowly than another, the rays are refracted closer to the normalrefracted closer to the normal

Causes pools and ponds to appear Causes pools and ponds to appear shallower than they are since the speed of shallower than they are since the speed of light is changed when the light waves light is changed when the light waves move from air into watermove from air into water

Refraction of LightRefraction of Light

AtmosphericAtmospheric Mirages Mirages

very hot air close to the ground very hot air close to the ground causes causes a speeding up and bending of a speeding up and bending of light waves, light waves, producing an imageproducing an image

image would appear upside down to image would appear upside down to the observer just as if it were reflected the observer just as if it were reflected off of water, but it is refractedoff of water, but it is refracted

Snell’s LawSnell’s Law

nn11sinsin11 = n = n22sinsin22

n n index of refraction index of refraction

11 angle of incidence angle of incidence

22 angle of refraction angle of refraction